This study was undertaken to determine whether the gravimetric method provided an accurate measure of water flux correction and to compare the gravimetric method with methods that employ nonabsorbed markers (eg, phenol red and were co-perfused in situ through the jejunum of 9 anesthetized rats (single-pass intestinal perfusion [SPIP]). Water absorption was determined from the phenol red, 14 C-PEG-3350, and gravimetric methods. The absorption rate constant (k a ) for Compound I was calculated. Both phenol red and 14 C-PEG-3350 were appreciably absorbed, underestimating the extent of water flux in the SPIP model. The average ± SD water flux (μg/h/cm) for the 3 methods were 68.9 ± 28.2 (gravimetric), 26.8 ± 49.2 (phenol red), and 34.9 ± 21.9 ( 14 C-PEG-3350). The (average ± SD) ka for Compound I (uncorrected for water flux) was 0.024 ± 0.005 min -1 . For the corrected, gravimetric method, the average ± SD was 0.031 ± 0.001 min -1 . The gravimetric method for correcting water flux was as accurate as the 2 "nonabsorbed" marker methods.

No abstract

The CK models may be useful to screen those ER formulations with unacceptable acute damage due to immediately available components. However, to evaluate potential delayed effects from ER formulations, the long-term model RbLV was still recommended.

Due to ease, number of animals, time and intrinsic mechanism, we concluded that for most formulations, 2 and 4 hr RtCK data alone should be reasonably predictive of muscle damage.